Seat assembly including a mechanical strut and machine using same

ABSTRACT

A machine includes a seat assembly and a mechanical strut attached to the seat assembly. The mechanical strut, free of pneumatic seals, is positioned to move at least a portion of an armrest of the seat assembly along a horizontal axis. A length adjustment mechanism is movable to release a friction lock mechanism within the mechanical strut. The mechanical strut is telescopically movable through a continuous range of armrest lengths when the friction lock mechanism is released.

TECHNICAL FIELD

The present disclosure relates generally to a seat assembly having atleast one armrest, and more particularly to a length adjustmentmechanism for releasing a friction lock mechanism of a mechanical strut,thereby allowing adjustment of a portion of the armrest through acontinuous range of lengths.

BACKGROUND

Adjustment devices, including pneumatic and mechanical struts, are usedin a number of applications. According to one example, an adjustmentdevice includes a finite number of notches or teeth at which the devicemay be locked. Specifically, U.S. Publication No. 2006/0000656 teaches aseat having an armrest that is movable to one of a finite number ofarmrest lengths. Specifically, an operator can pull on an arm positionlock release that will move a spring loaded pin from one of a finitenumber of arm position bores. Once the operator has selected anappropriate armrest length, the operator may release the arm positionlock release and allow the pin to reinsert itself within one of the armbores.

An alternative adjustment device may include a well known gas strut. Agas strut may provide adjustment through a continuous range ofpositions; however, because a gas strut requires seals, it issusceptible to leaks of pressurized gas during operation. Suchpressurized gas leaks, if not addressed, may lead to ultimate failure ofthe strut.

The present disclosure is directed to one or more of the problems setforth above.

SUMMARY OF THE DISCLOSURE

In one aspect, a machine includes a seat assembly and a mechanical strutattached to the seat assembly. The mechanical strut, free of pressurizedgas, is positioned to move at least a portion of an armrest of the seatassembly along a horizontal axis. A length adjustment mechanism ismovable to release a friction lock mechanism within the mechanicalstrut. The mechanical strut is telescopically movable through acontinuous range of armrest lengths when the friction lock mechanism isreleased.

In another aspect, a method of moving at least a portion of an armrestof a seat assembly along a horizontal axis includes a step of actuatinga length adjustment mechanism of the armrest to release a friction lockmechanism of a mechanical strut. The portion of the armrest is thenmoved through a continuous range of armrest lengths. The lengthadjustment mechanism is released to engage the friction lock mechanismof the mechanical strut.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side diagrammatic view of a machine according to the presentdisclosure;

FIG. 2 is a perspective view of a steering column assembly of themachine of FIG. 1;

FIG. 3 is a side diagrammatic view in cross section of a mechanicalstrut of the steering column assembly of FIG. 2;

FIG. 4 is an isometric view of a first locking member of a friction lockmechanism according to the present disclosure;

FIG. 5 is an isometric view of a second locking member of a frictionlock mechanism according to the present disclosure;

FIG. 6 is a perspective view of a seat assembly of the machine of FIG.1;

FIG. 7 is a side diagrammatic view of an armrest of the seat assembly ofFIG. 6;

FIG. 8 is a side diagrammatic view in cross section of the mechanicalstrut of FIG. 3 in a retracted position; and

FIG. 9 is a side diagrammatic view in cross section of the mechanicalstrut of FIG. 3 in an expanded position.

DETAILED DESCRIPTION

An exemplary embodiment of a machine 10 is shown generally in FIG. 1.The machine 10 may be a wheel loader, as shown, or any other machine orvehicle having an operator control station 12. The operator controlstation 12 is mounted to a body 14 of the machine 10 and may include asteering column assembly 16 and a seat assembly 18. The operator controlstation 12 may include various other devices, including, but not limitedto, one or more machine operation controllers (shown in FIG. 6). Forexample, a machine operation controller may be provided for controllingmovement of an implement 20, such as a bucket, of the machine 10.

The steering column assembly 16 is shown generally in FIG. 2, andincludes a steering column 22 and a base 24 for a steering wheel 26. Thesteering column 22 may include one or more columns, such as, forexample, columns 28 and 30. The steering column assembly 16 alsoincludes a mechanical strut 32. The mechanical strut 32 includes aninner tube 34 and an outer tube 36 having a slightly larger diameterthan inner tube 34. The outer tube 36 is configured to telescopicallyreceive the inner tube 34 and may provide a continuous range of lengthsbetween a fully expanded length and a fully retracted length of themechanical strut 32. In some configurations, the inner and outer tubes34 and 36 may have a substantially uniform circular cross-section.Alternatively, the inner and outer tubes 34 and 36 may have otheruniform or non-uniform cross sections.

A guard member 38, which is something other than a pneumatic seal, maybe provided over a distal end 40 of the outer tube 36. The guard member38 may prevent dust and various other airborne particles from enteringthe outer tube 36 via an external surface of the inner tube 34 when theinner tube 34 is being telescopically received within the outer tube 36.Guard member 38 may have substantially the same diameter as the innertube 34, and may be made of any material, including, but not limited, toa plastic or rubber.

The outer tube 36, at a first attachment end 42 of the mechanical strut32, may be pivotably attached to the steering wheel base 24.Specifically, the outer tube 36 may pivot about a pin 48 that extendsthrough each of the first plate 44, a first end 50 of the outer tube 36,and the second plate 46. The inner tube 34, at a second attachment end52 of the mechanical strut 32, may be pivotably attached to a portion ofthe steering column 22, such as column 28. More specifically, the innertube 34 may pivot about a pin 58 extending through each of a first plate54, a first end 60 of the inner tube 34, and a second plate 56. Thefirst end 60 of the inner tube 34 may also include a trigger 62 forreleasing a friction lock mechanism (shown in FIG. 3) of the mechanicalstrut 32.

Although the outer tube 36 is shown pivotably attached to the steeringwheel base 24 and the inner tube 34 is shown pivotably attached tocolumn 28 of the steering column 22, it should be appreciated that eachof the outer tube 36 and the inner tube 34 may be attached to any partof the steering column assembly 16. For example, it may be desirable topivotably attach the outer tube 36 to column 28 and the inner tube 34 tocolumn 30. The positioning of mechanical strut 32, it should beappreciated, will determine the location of the axis about which aportion of the steering column assembly 16 will rotate.

A configuration of the mechanical strut 32 is shown in greater detail inFIG. 3. Specifically, a cross section of the mechanical strut 32illustrates the friction lock mechanism 70. The friction lock mechanism70 includes a first locking member 72 and a second locking member 74that may include a substantially frustoconical shape, as shown. Thefirst locking member 72 may be fixedly attached to a distal end 76 ofthe inner tube 34 and may include a structure having at least onefinger, such as, for example, fingers 78 and 80, for receiving thesecond locking member 74. Engagement of the first and second lockingmembers 72 and 74 forces at least one of fingers 78 and 80 of the firstlocking member 72 into frictional engagement with an inner surface 82 ofthe outer tube 36, thereby preventing telescopic movement of themechanical strut 32. This configuration of the friction lock mechanism70 may be referred to as an engaged configuration.

The first locking member 72 of the friction lock mechanism 70 can beseen generally in FIG. 4. Fingers 78 and 80 may extend from a base 90that is fixedly attached to the distal end 76 of inner tube 34. Base 90may also include an opening 92. A slot 94, or gap, between fingers 78and 80 may also be provided for receiving a key, as described below. Thesecond locking member 74 of the friction lock mechanism 70 can be seengenerally in FIG. 5. Second locking member 74 may also include anopening 96 and a slot 98 for receiving a key.

Referring again to FIG. 3, a first spring 100 and a second spring 102may provide a desired amount of resistance when the mechanical strut 32reaches a fully extended or a fully retracted position in order toprotect internal components of the mechanical strut 32. Thus, springs100 and 102 may only come into play when mechanical strut 32 isapproaching one of its extreme positions as shown in FIGS. 8 and 9, butare otherwise uncompressed. Alternatively, first and second springs 100and 102 may bias the first locking member 72 and the second lockingmember 74 into engagement and, as a result, into frictional engagementwith the outer tube 36. Specifically, at least one of the fingers 78 and80 may frictionally engage the inner surface 82 of the outer tube 36.

A tilt adjustment mechanism 104 may include trigger 62 pivotablyattached to an attachment end of the mechanical strut 32, such as thesecond attachment end 52, for moving the second locking member 74 out ofengagement with the first locking member 72 and into a releasedconfiguration. A key 110 may be positioned within at least a portion ofeach of the first locking member 72 and the second locking member 74 forpreventing one of the first and second locking members 72 and 74,respectively, from rotating relative to the other. For example, the key110 may be positioned within slot 94 of the first locking member 72 andslot 98 of the second locking member 74.

A threaded member 112 includes a first end 114 having a notch thatreceives a portion of the trigger 62 so that threaded member 112 isprevented from rotating. The threaded member 112 is movable along alinear axis within the inner tube 34 in response to movement of thetrigger 62. A second end 116 of the threaded member 112, having threads118 on the exterior thereof, is configured to engage a spiral patternedprotrusion 120 extending from an internal surface 122 of a first end 124of an elongate sleeve 126 provided within the inner tube 34. The spiralpatterned protrusion 120 may, alternatively, include a series ofbearings positioned within one or more spiral patterned grooves withinthe internal surface 122 of the sleeve 126. When the threaded member 112is moved in a linear direction, via actuation of the trigger 62, threads118 of the threaded member 112 engage the spiral patterned protrusion120 of the sleeve 126 and cause the sleeve 126 to rotate about thelongitudinal axis of the mechanical strut 32. It should be appreciatedthat a portion 128 of the trigger 62 may extend into the first end 114of the threaded member 112 to prevent the threaded member 112 fromrotating, but other strategies that prevent rotation are also within thescope of the present disclosure.

A second end 130 of the sleeve 126 includes a hexagonal shaped bore 132therethrough for receiving a rod 134. The rod 134 includes a hexagonalshaped first end 136 extending through the bore 132 and a second end 138threadably attached to the second locking member 74, such as by athreaded engagement. Rotational movement of the sleeve 126, therefore,causes rotational movement of the rod 134. It should be appreciated thatthe rod 134 also extends through the opening 92 of the first lockingmember 72 and may include a pair of annular shoulders, such as 134 a and134 b, for limiting the linear movement of the first locking member 72with respect to rod 134.

The key 110 is positioned within at least a portion of each of the firstlocking member 72 and the second locking member 74 for preventing one ofthe first locking member 72 and the second locking member 74 fromrotating relative to the other. The key 110 prevents the rotationalmovement of the rod 134 from rotating the second locking member 74 and,indirectly, the first locking member 72, and causes the second lockingmember 74 to move in a linear direction into and out of engagement withthe first locking member 72 based on a rotational direction of the rod116. A spring 139 may be provided within inner tube 34 or sleeve 126 forbiasing the threaded member 112 and, indirectly, the trigger 62 towardthe attachment end 52. When biased in such a manner, the trigger 62remains in a non-actuated position.

It should be appreciated that the spring 139 is provided with sufficientpreload to force the threaded member 112 toward the second attachmentend 52, thereby rotating the sleeve 126 and rod 116 in an oppositedirection and pulling the second locking member 74 into engagement withthe first locking member 72. Engagement of the first and second lockingmembers 72 and 74 forces at least one of fingers 78 and 80 of the firstlocking member 72 into frictional engagement with an inner surface 82 ofthe outer tube 36, thereby preventing telescopic movement of themechanical strut 32. Actuating the trigger 62 acts against the force ofthe spring 139 to move the friction lock mechanism 70 from the engagedconfiguration to the released configuration.

According to an alternative embodiment, the mechanical strut 32 may beused in the seat assembly 18 of machine 10. The seat assembly 18 isshown in FIG. 6 and includes a frame 140 to which a first armrest 142, asecond armrest 144, a seat 146, and a back 148 are attached. The seatassembly 18 may also include one or more machine operation controllers,such as controllers 150 and 152, pivotably attached to the first armrest142 and second armrest 144, respectively. Controllers 150 and 152 may beused to control various operations of the machine 10. For example,controller 150 may be used to control movement of the implement 20 ofthe machine 10.

Turning now to FIG. 7, the first armrest 142 is shown in greater detail.The armrest 142 may include a first portion 160 and a second portion162. The second portion 162 may include controller 150. Mechanical strut32, as described above, may be positioned within the armrest 142, asshown, to move the second portion 162 of the armrest 142 along ahorizontal axis. Specifically, the outer tube 36 of the mechanical strut32, at the first attachment end 42, may be attached to the first portion160 of the armrest 142. The inner tube 34 of the mechanical strut 32, atthe second attachment end 52, may be attached to the second portion 162of the armrest 142. A length adjustment device 164, which may includethe controller 150, may actuate the trigger 62 of the mechanical strut32 to move the friction lock mechanism 70 to a released configuration,as described above. For example, movement of the controller 150 about ahorizontal axis may release the friction lock mechanism 70 and allowmovement of the second portion 162 of the armrest 142 through acontinuous range of armrest lengths.

According to a further example, it may be desirable to provide anadditional telescoping member within the armrest 142 that runs parallelto the mechanical strut 32. An additional telescoping member may includeonly an inner and outer tube, such as inner and outer tubes 34 and 36,and may be free of a locking mechanism, such as the friction lockmechanism 70 of mechanical strut 32. The additional telescoping membermay provide additional support for the first and second portions 160 and162 of the armrest 142. It should be appreciated that various devicesmay be used in conjunction with the mechanical strut 32.

INDUSTRIAL APPLICABILITY

Adjustment devices are used in a number of applications, includingvarious applications within an operator control station 12 of a machine10. Specifically, adjustment devices may be used for adjusting steeringcolumn assemblies, seat assemblies, operation controllers, and variousother devices to allow for different operator preferences. According tosome applications, adjustment devices allow positioning of a componentto one of a finite number of adjustment positions. Although thesedevices may be effective, they offer only a limited range of motion ofthe device.

Gas struts may provide for the desired range of positions in variousapplications; however, because a gas strut requires seals, it issusceptible to leaks during operation. Such leaks, if not addressed, maylead to ultimate failure of the strut. Utilizing the mechanical strut 32of the present disclosure for adjustment of a steering column assembly16, a seat assembly 18, or other adjustable component provides acontinuous range of potential positions available to the operator,without the known problems associated with gas struts. In addition, foradjustable components, such as, for example, a steering column assembly,currently utilizing a gas strut, the mechanical strut 32, free ofpressurized gas, may replace the gas strut as a retrofit requiringminimal changes. It should, therefore, be appreciated that themechanical strut 32 of the present disclosure finds potentialapplication anywhere a gas strut is currently being used.

The mechanical strut 32, as shown in FIG. 3, includes an inner tube 34and an outer tube 36. The outer tube 36 is configured to telescopicallyreceive the inner tube 34 and provide a continuous range of lengthsbetween a fully expanded length and a fully retracted length of themechanical strut 32. A trigger 62 is provided for releasing a frictionlock mechanism 70 of the mechanical strut 32. The friction lockmechanism 70 includes a first locking member 72 and a second lockingmember 74. The first locking member 72 may be fixedly attached to adistal end 76 of the inner tube 34 and may include a structure having aleast one finger, such as, for example, fingers 78 and 80, for receivingthe second locking member 74. Biased engagement of the first and secondlocking members 72 and 74 forces at least one of the fingers 78 and 80of the first locking member 72 into frictional engagement with an innersurface 82 of the outer tube 36, thereby preventing telescopic movementof the mechanical strut 32.

The trigger 62 may be actuated for moving the second locking member 74out of engagement with the first locking member 72, and moving thefriction lock mechanism 70 into a released configuration. Specifically,the threaded member 112 is movable along a linear axis within the innertube 34 in response to movement of the trigger 62. A second end 116 ofthe threaded member 112, having threads 118 on the exterior thereof, isconfigured to engage a spiral patterned protrusion 120 extending from aninternal surface 122 of a first end 124 of an elongate sleeve 126provided within the inner tube 34.

When the threaded member 112 is moved in a linear direction, threads 118of the threaded member 112 engage the spiral patterned protrusion 120 ofthe sleeve 126 and cause the sleeve 126 to move in a rotationaldirection. A second end 130 of the sleeve 126 includes a hexagonalshaped bore 132 therethrough for receiving a rod 134. The rod 134includes a hexagonal shaped first end 136 extending through the bore 132and a second end 138 fixedly attached to the second locking member 74,such as by a threaded engagement. Rotational movement of the sleeve 126,therefore, causes rotational movement of the rod 134.

The key 110 is positioned within at least a portion of each of the firstlocking member 72 and the second locking member 74 for preventing one ofthe first locking member 72 and the second locking member 74 fromrotating relative to the other. The key 110 prevents the rotationalmovement of the rod 116 from rotating the second locking member 74 and,indirectly, the first locking member 72, and causes the second lockingmember 74 to move in a linear direction and out of engagement with thefirst locking member 72.

This ultimately moves the second locking member 74 out of engagementwith the first locking member 72 and allows the mechanical strut 32 tobe continuously adjusted between a fully extended length and a fullyretracted length. By translating the linear motion caused by the trigger62 to rotational motion and the rotational motion back to linear motion,it should be appreciated that greater precision may be achieved. Forceapplied to the trigger 62 may be controlled through the translation, andthe second locking member 74 may be moved out of engagement with thefirst locking member 72 only the amount necessary to move the firstlocking member 72 out of frictional engagement with the inner surface 82of the outer tube 36. It should also be appreciated that the threadedmember 112 will be moved a first distance and the second locking member74 will be moved a second distance that is less than the first distance.

Spring 139 may be provided within inner tube 34 or sleeve 126 forbiasing the threaded member 112 and, indirectly, the trigger 62 towardthe second attachment end 52. When biased in such a manner, the trigger62 remains in a non-actuated position. Alternatively, springs 100 and102 may be provided to bias the first and second locking members 72 and74 into engagement. By biasing the first and second locking members 72and 74 into engagement, the rod 134, threaded member 112, and sleeve 126are moved toward attachment end 52, thereby returning the trigger 62 toa non-actuated position.

According to a first example, shown in FIG. 2, the trigger 62 may beactuated to release the friction lock mechanism 70 of the mechanicalstrut 32, as described above. When the friction lock mechanism 70 isreleased, the steering wheel 26, at base 24, and/or the steering column22 may be tilted about a horizontal axis. When the base 24 is tiltedupward, it should be appreciated that the inner tube 34 may telescopewithin the outer tube 36 to shorten the length of the mechanical strut32. FIG. 8 shows the mechanical strut 32 at a fully retracted, orshortened, length. Alternatively, when the base 24 is tilted downward,it should be appreciated that the inner tube 34 may be telescoped out ofthe outer tube 36 to provide a greater length of the mechanical strut32. A fully expanded length of the mechanical strut 32 is illustrated inFIG. 9. When the operator has selected a desired tilt position, thetrigger 62, or additional tilt adjustment mechanism 104 connected to thetrigger 62, may be released to frictionally engage the friction lockmechanism 70 and prevent further telescopic movement of the mechanicalstrut 32. Specifically, the biased engagement of the first and secondlocking members 72 and 74 is allowed, and the first locking member 72frictionally engages the inner surface 82 of the outer tube 36 to lockthe steering wheel base 24 at the selected position.

According to a second example, shown in FIG. 7, the controller 150,attached directly or indirectly to the trigger 62, may be actuated torelease the friction lock mechanism 70 of the mechanical strut 32. Whenthe friction lock mechanism 70 is released, such as by tilting thecontroller 150, the second portion 162 of the armrest 142 is adjustablethrough a continuous range of armrest lengths, i.e., the second portion162 is movable along a horizontal axis. When the second portion 162 ismoved toward the first portion 160, it should be appreciated that theinner tube 34 may telescope within the outer tube 36 to shorten thelength of the mechanical strut 32. FIG. 8 shows the mechanical strut 32at a fully retracted, or shortened, length. Alternatively, when thesecond portion 162 is moved away from the first portion 160, it shouldbe appreciated that the inner tube 34 may be telescoped out of the outertube 36 to provide a greater length of the mechanical strut 32. A fullyexpanded length of the mechanical strut 32 is illustrated in FIG. 9.When the operator has selected a desired armrest length, the controller150, connected to the trigger 62, may be released to frictionally engagethe friction lock mechanism 70 and prevent further telescopic movementof the mechanical strut 32.

Although specific examples have been given, it should be appreciatedthat the mechanical strut 32 of the present disclosure will find use innumerous applications, including, but not limited to, applications inwhich continuous adjustment of a component is desired. Specifically, themechanical strut 32, including the friction lock mechanism 70, isadjustable through a continuous range of lengths between a fullyexpanded length, as shown in FIG. 9, and a fully retracted length, asshown in FIG. 8.

It should be understood that the above description is intended forillustrative purposes only, and is not intended to limit the scope ofthe present disclosure in any way. Thus, those skilled in the art willappreciate that other aspects of the disclosure can be obtained from astudy of the drawings, the disclosure and the appended claims.

1. A machine, comprising: a seat assembly; a mechanical strut attachedto the seat assembly and positioned to move at least a portion of anarmrest of the seat assembly along a horizontal axis, wherein themechanical strut is free of pressurized gas; a length adjustmentmechanism movable to release a friction lock mechanism which includes afrustoconical shape, within the mechanical strut; and wherein themechanical strut is telescopically movable through a continuous range ofarmrest lengths when the friction lock mechanism is released.
 2. Themachine of claim 1, further including at least one machine operationcontroller pivotably attached to the armrest.
 3. The machine of claim 2,wherein the mechanical strut includes a first attachment end attached toa first portion of the armrest and a second attachment end attached to asecond portion of the armrest, and wherein the controller is attached tomove with the second portion of the armrest.
 4. The machine of claim 3,wherein the length adjustment mechanism includes at least a portion ofthe machine operation controller.
 5. A machine, comprising: a seatassembly; a mechanical strut attached to the seat assembly andpositioned to move at least a portion of an armrest of the seat assemblyalong a horizontal axis, wherein the mechanical strut is free ofpressurized gas; a length adjustment mechanism movable to release afriction lock mechanism within the mechanical strut; wherein themechanical strut is telescopically movable through a continuous range ofarmrest lengths when the friction lock mechanism is released; and aguard member extending over a distal end of an outer tube of themechanical strut and including an opening therethrough for receiving aninner tube of the mechanical strut.
 6. The machine of claim 5, furtherincluding a first locking member of the friction lock mechanism attachedto a distal end of the inner tube and configured to receive a secondlocking member.
 7. The machine of claim 6, wherein the first lockingmember includes at least one movable finger for receiving asubstantially frustoconical shape of the second locking member.
 8. Themachine of claim 7, further including at least one spring for biasingthe first and second locking members into engagement, wherein the secondlocking member is configured to move at least a portion of the firstlocking member into frictional engagement with an inner surface of theouter tube during engagement.
 9. The machine of claim 8, wherein thelength adjustment mechanism includes a trigger pivotably attached to anattachment end of the inner tube for moving the second locking memberout of engagement with the first locking member.
 10. The machine ofclaim 9, further including a threaded member having a first endpositioned within the trigger and a second end having external threadson a portion thereof, wherein the threaded member is movable within theinner tube along a linear axis in response to movement of the trigger.11. The machine of claim 10, further including an elongate sleeve havinga first end including a spiral patterned protrusion on an internalsurface thereof and a second end having a hexagonal shaped boretherethrough, wherein linear movement of the threaded member causes theexternal threads of the threaded member to engage the spiral patternedprotrusion of the elongate sleeve and cause rotational movement thereof.12. The machine of claim 11, further including a rod having a hexagonalshaped first end extending through the hexagonal shaped bore of theelongate sleeve and a second end threadably attached to the secondlocking member, wherein rotational movement of the elongate sleevecauses rotational movement of the rod.
 13. The machine of claim 12,further including a key positioned within at least a portion of each ofthe first locking member and the second locking member for preventingone of the first locking member and the second locking member fromrotating relative to the other, wherein rotational movement of the rodcauses linear movement of the second locking member.
 14. A method ofmoving at least a portion of an armrest of a seat assembly along ahorizontal axis, comprising: actuating a length adjustment mechanism ofthe armrest to release a friction lock mechanism of a mechanical strut;moving the portion of the armrest along an axis through a continuousrange of armrest lengths; releasing the length adjustment mechanism toengage the friction lock mechanism of the mechanical strut; and movementof the friction lock mechanism includes translating rotational motionabout the axis into linear motion along the axis.
 15. The method ofclaim 14, wherein the actuating step includes tilting a machineoperation controller of the armrest about the horizontal axis.
 16. Themethod of claim 15, wherein the moving step includes moving a portion ofthe armrest including the machine operation controller.
 17. The methodof claim 15 wherein the step of tilting the machine operation controllerincludes adjusting a length of the mechanical strut to one of acontinuous range of lengths between a fully extended length and a fullyretracted length.
 18. A method of moving at least a portion of anarmrest of a seat assembly along a horizontal axis, comprising:actuating a length adjustment mechanism of the armrest to release afriction lock mechanism of a mechanical strut; moving the portion of thearmrest through a continuous range of armrest lengths; and releasing thelength adjustment mechanism to engage the friction lock mechanism of themechanical strut; biasing at least one of a first locking member of thefriction lock mechanism and a second locking member of the friction lockmechanism into engagement with the other; and moving the first lockingmember into frictional engagement with an inner surface of themechanical strut.
 19. The method of claim 18, wherein the actuating stepincludes: moving a threaded member along a linear axis; and causingexternal threads of the threaded member to engage a spiral patternedprotrusion of an elongate sleeve and cause rotational movement thereof.20. The method of claim 19, wherein the actuating step further includes:causing a hexagonal shaped bore of the elongate sleeve to engage ahexagonal shaped portion of a rod and cause rotational movement thereof;and preventing one of the first and second locking members from rotatingrelative to the other in response to rotational movement of the rod,thereby causing linear movement of the second locking member.